It was a physically arduous six-month shoot for a massive tentpole film, replete with swamp-wading and swordfighting. And right before filming began on Pirates of the Caribbean: On Stranger Tides, Cruz discovered buried treasure of a different sort.

"I was pregnant through the whole movie. I found out at the beginning," says Cruz, who, with her typical directness, immediately broke the news to Depp and director Rob Marshall. "I found out before we started, and I wanted them to know because I did not want to go in with any secrets, for protection and for the honesty of my relationship with them. For six months they were all taking such good care of me."

It helped that Cruz, 37, handled her pregnancy with pirate-worthy panache, having little morning sickness, nausea or dizziness. She avoided any dangerous stunts in the film, which opens today, and relied heavily on her dance background to learn the intricate fight choreography required of her mercenary buccaneer Angelica, who's vying with Depp's Jack Sparrow to find the Fountain of Youth.

For Cruz, it felt "good to be working" while expecting, she says. "I had a lot of free days, and once in a while, I had a free week. (The shoot) was very balanced, very easy. I traveled around the world. The whole summer I spent in Hawaii. It was good. I have only good memories" of the shoot.

Fast-forward to a May morning in Manhattan. Cruz's infant son Leo, born at the end of January (Dad is her husband, Oscar-winning actor Javier Bardem), is asleep upstairs in her hotel room while she sips tea in the downstairs lounge and carefully monitors her BlackBerry, waiting for a call letting her know he's awake and ready to eat. The Spanish actress could be the poster girl for fecund, ripe motherhood— all chocolaty brown eyes, voluptuous lips and cascades of coffee-colored hair, coupled with curves in all the right places.

"She looks like she never had a child. She says it just came off, but no, she works at it," Marshall says. "She has a dancer's discipline and doesn't reach for the bread."

Cruz is a knockout, no question. But, Marshall says, "She refuses to be defined by that. She's a great actor who likes to be challenged. In Pirates, she had to be physical and tougher and more masculine. I think it was fortuitous there was this masculine energy in her to play this character — this pirate Bardem in there with her to help her."

High-seas sparring

For Cruz, who had most recently appeared in more arty films like 2008's Elegy and 2009's Nine— and had a cameo in last year's Sex and the City sequel — playing a fortune-hunter was a pure adrenaline-laden romp. Plus, she got to spar with Depp's devious Jack Sparrow.

"The character is full of contradictions. To explore the pirate mentality was a lot of fun for me. She has to be a great manipulator. A great liar. She has to make Jack Sparrow believe whatever she wants him to believe," Cruz says. "She has a desire for revenge. She also has this religious background. She says Jack Sparrow corrupted her and took her out of the convent. She doesn't trust men."

Is she anything like Angelica? "We are both pretty stubborn. We want something, we go after it. But I don't ask myself 'Do I need to be like that character?' I just need to understand why they behave a certain way."

When she told Marshall and Depp about her pregnancy, both didn't waver in their support because, Marshall says, they knew she was worth it.

Marshall shot as many of her big scenes as possible at the start of the film, before Cruz was really showing. Her costumes were modified each month to accommodate her growing girth. "She had a corset that was elasticized and could move with her. She's so physical that she wanted to do more, and we kept telling her no," Marshall says. "She's a perfectionist."

But she's not quite as single-minded about her career as she used to be. For Cruz, personal connections are everything, professionally and personally. She selects projects based as much on the caliber of the script as the people working on the film. It's why she immediately said yes to shooting with Marshall and Depp.

Quality of life is paramount.

"To be able to work with kind people, good people, is as important as how talented they are. Maybe at the beginning you don't care about that as much. I take that more and more into account every day," she says. "The older I am, the more I care about that."

She seems to draw people to her, and those who have worked with her come back for seconds, thirds or, in the case of frequent collaborator Pedro Almod?var, fourths.

Marshall directed Cruz in 2009's Nine and offered her the part in Pirates over dinner in London, before Nine was complete. Depp had collaborated with her on the 2001 drama Blow. This fall, she's reuniting with Don't Move's Sergio Castellitto for a film based on Margaret Mazzantini's novel Venuto al mondo. Woody Allen, who directed Cruz to an Oscar for 2008's Vicky Cristina Barcelona, asked her to be in his next film, Bop Decameron.

"She's a great natural actress, and she has great excitement on the screen. I don't have to do any work," the director says .

What is it about Cruz that inspires such loyalty? "She's got this great vibe to her," says Nicole Kidman, who co-starred with Cruz in Nine.

Salma Hayek, a longtime confidante, calls Cruz "a great friend — not just to me but to everybody who's friends with her. She's funny as hell, entertaining, kind, sweet, consistent. She's an amazing woman. It's nice to have a friend who's inspiring. She has a very strong, powerful mind. She's able to juggle so many things so well. She knows what she wants. And things come to her, because she deserves them. It's a karma thing."

In person, Cruz is thoughtful and methodical, not one to banter or crack wise. She's wary during interviews, unwilling to be warm and fuzzy with reporters or to dish out spontaneous anecdotes about her personal life. She thinks before she speaks, and she carefully considers her response to every question.

"She's a huge star but she's incredibly private," Kidman says. "Look at how she slipped away and married Javier. She's able to manage it — it comes from having a supportive, strong family."

Public vs. private life

But when Cruz feels comfortable, she's lighter, funnier and more relaxed, joking that she has gone from her usual heavy reading to piles of baby books, which have become her literary passion.

She politely but firmly declines to discuss her child with the press.

"I'm very determined to keep the privacy of my son, to keep that as intact as possible because he has that right. I like to not make a big deal. It's very important to me. And that's one of the reasons I don't talk about my son in interviews. It's natural protection."

Cruz and Barden even managed to have their baby in paparazzi-laden Los Angeles without anyone being the wiser. How did they pull it off?

"If I told you, then people would know," Cruz says with a laugh. "I've always tried to separate my work from my private life. And I never felt that I had to apologize for that. That's my right. I take my right. If not, nobody is going to do that for you."

Her priorities have changed, but that shift happened several years ago, before she was married and a mother. After her Oscar-nominated turn in Almod?var's 2006 quirky dramedy Volver, Cruz went from workaholic to more of a homebody, doing a movie or two a year, no more, and opting to spend time with her siblings and significant other.

"I was choosing in a different way because I was starting to value more the time for myself. That change happened a few years ago, so it's no different now. I try to go for the projects that really make me feel something," she says. "You are interested and curious about that personality and story and world. Without that, there is no passion."

"Woody (Allen) offered me the movie, and it's two-three weeks in Rome, in the summer. It's a two-hour flight to Madrid," says Cruz, who has homes there and in California. "I will see how it's going. I can't make a plan now that this is my next two years. My priority is my son. I will see it as it comes."

And how about the fact that someday, Leo will get to see his mom be a fierce and fearless pirate on screen and maybe even play with the Angelica action figure?

"Yeah, I already thought of that," she says with a smile. "That makes me happy."

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